Microplastic Abundance in the Locally Produced Commercial Compost and the Characteristics

Abstract

Compost is a widely used soil amendment in the agricultural sector in Sri Lanka. Applying compost could improve soil quality, and it is used in reclaiming degraded agricultural lands. However, low grade compost that contains pollutants may have adverse effects on the quality of the agro-ecosystem. Microplastic is a possible contaminant that can be moved into the agro-ecosystem through poor quality compost application. The present study was conducted to assess the microplastic availability and characteristics of locally produced municipal solid waste and agricultural waste compost. Representing commercial scale agricultural and municipal solid waste composting facilities; twenty compost samples with three replicates were obtained for microplastic identification. A combination of methods (manual separation, oxidation digestion plus density separation) was used to separate and detect microplastics from compost samples. This study revealed that; microplastics are present in agricultural and municipal solid waste compost. Municipal solid waste compost contained significantly (p<0.05) higher microplastic than agricultural waste compost (on average 0.63% and 0.033%, respectively). Average amount of soft plastic content in municipal solid waste compost and agricultural waste compost (1321 items/kg and 71 items/kg, respectively) were higher than the hard plastics (388 items/kg and 37 items/kg, respectively). The study confirmed that compost could act as a carrier of microplastics in agricultural ecosystems. It can be recommended that quality standards should be implemented to minimize the microplastic content in compost and the code of practices for municipal solid waste compost production should be updated to control microplastic contamination to safeguard the quality of agro-ecosystems.